ch. 2 questions - neutrons and thus differing in atomic...

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Jackie Daa Biology 1151 M-W-Th 8:00-9:50 Robinson Chapter 2 Questions 1. An element is a substance that cannot be broken down to other substances by chemical reactions. 2. 25 out of the 92 naturally-occurring elements are known to be essential to life a. Carbon, Hydrogen, Oxygen, and Nitrogen make up 96% of living matter. b. Calcium, Phosphorus, Potassium, Sulfur, Sodium, Chlorine, Magnesium and trace elements make up the other 4%. 3. Trace elements are those required by an organism in only very small amounts, such as iron. 5. A proton and a neutron have about the same mass of 1.7x10 -24 gram, or 1 Dalton. An electron’s mass is 1/2000 th of a proton or neutron. 6. An isotope is one of several atomic forms of an element, each containing a different number of
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Unformatted text preview: neutrons and thus differing in atomic mass. 7. Radioactive tracers may be used in biology and medicine by following atoms through metabolism and/or any other chemical processes in the body like cells making copies of their DNA. Also, the tracers can be used to diagnose certain disorders of organs and blood and they can be used in imaging instruments like PET scanners. 8. An electron shell represents an energy level as the distance of an electron from the nucleus of an atom. 9. Only 2 electrons may be in the first electron shell. 10. Up to 8 electrons may be in the second and subsequent shells. 11. Yes, the electrons are orbiting the nucleus in concentric circles....
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